This invention relates to radon detection and more specifically to a system whereby radon level readings may be accurately and reliably obtained within the test site of a structure without the need for direct supervision during the test.
Radon is a colorless, odorless, radioactive gas, which like other radioactive elements, decays or changes into smaller particles termed progeny which, if inhaled either directly or when attached to dust particles or the like, may emit radioactivity directly into one's lung and thus cause cancer. It is, accordingly, important to determine the radon level present in one's house so that steps can be taken to alleviate or eliminate the problem, if it exists. Normally, radon seeps into the basement of the house or other structure through the supporting ground or from water contained therein. Thus the normal test method for determining radon level in such a structure is to place a radon detector, normally the activated charcoal type, in the basement and to permit such to be bombarded by the ambient air for a time period generally between three and seven days. The test is started by removing a closure member from the charcoal canister and terminated by replacing such member to seal the container after the test. Other methods and devices currently utilized for testing radon and its decay products in buildings include continuous radon monitors, alpha-track detectors, grab sampling devices, and radon progeny integrating sampling units. Procedures and references for these various methods can be found in numerous U.S.E.P.A. publications, e.g., EPA 520/1/-86-03 entitled "Implementation Strategy for the Radon/Radon Progeny Measurement Proficiency Evaluation and Quality Assurance Program." Another information source in non-technical terms is that article entitled "Radon Detectors" Pages 440 through 447 of Consumer Reports, July 1987.
While these above-indicated detection systems are adequate within their technical limitations, they are inappropriate for legally sensitive radon tests, e.g., real estate transactions, because they are subject to tampering by interested parties. Thus, the importance of determining the radon level of a home planning to be purchased prior to completing such transaction is being recognized by an increasing number of lenders and purchasers. Accordingly, sales contracts may require a radon test to be done on the premises while the would be seller is still occupying the house. Generally such a contract would require that a test result below a certain radon level, normally expressed in picocuries of radiation per liter of air, be obtained. Since most such tests must be conducted over time to be accurate because the particular radon level may dramatically change over time, it is impractical for the tester or the purchaser's agent to be present over such lengthy time periods, say three to seven days. Accordingly, there is a need to provide a system in which the more practical methods of radon air analysis for house testing, i.e., charcoal canister or radon progeny integrating sampling units, can be conducted in a tamper-proof collection procedure which allows the test results to be guaranteed as true and accurate and free from tampering such that the test results can be contractually relied upon.
Accordingly, the primary object of the present invention is the provision of a system embodied in an easily transportable device which can monitor radon levels in a building when left unattended for days or weeks in a tamper-proof manner. These and other objects of the present invention are accomplished by a radon detector system for accurately measuring the radon level within a finite test site of a structure over a period of time without direct supervision by the tester comprising a portable fully enclosed housing having a lockable access cover and means for attaching said housing to a fixed member of said structure within said test site, said housing having a radon monitoring device in turn including an air accepting portion thereof disposed externally of said housing and both external and internal detection means for detecting various possible modes of tampering with said radon monitoring device and/or the test site in which such is disposed, said external detection means including: (a) first motion detection means for detecting the presence of a moving object adjacent said housing, and (b) test site air environment detection means for detecting a change in the air proximal to the housing, said internal detection means including: (a) second motion detection means for detecting movement of the housing, (b) means for detecting the interruption of electrical power to the housing, and (c) means for detecting removal or dislodoging of said air accepting portion of said monitoring device.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawing.